As an agricultural combine moves across a field, it cuts standing crop and feeds the severed crop materials to a threshing section of the combine. The threshing section of a rotary combine typically includes a threshing cylinder rotatably mounted within a foraminous housing. As the threshing cylinder rotates, the crop materials gently spiral rearwardly and grain is separated from the remainder of the crop materials. Material passing from the threshing cylinder gravitationally passes to a cleaning section of the combine for further processing.
The cleaning section of a rotary combine typically includes a pair of vertically spaced sieves. The sieves are horizontally oscillated causing clean grain to fall therethrough for collection. Normally, at least one of the sieves on the combine includes a plurality of “fingers” that are adjustable relative to each other such that the combine can operate in crop materials having different grains. A blower or fan directs air upwardly and across the sieves to further separate material other than grain from the materials passing from the threshing section.
As will be appreciated, heavier grain material falls through the sieves, is collected, and conveyed to a clean grain bin on the combine. Incompletely threshed grain, however, will not normally pass through the sieves and yet is too heavy to be blown out the rear of the combine with the chaff. These materials, which include grain, are commonly referred to as “tailings”. As an example, “tailings” include a fluffy or extremely light weight mixture of grain and mature vegetation on which the grain grows. In the case of wheat, barley and similar crop, tailings include the grain which remains attached to the fragments of the heads, while in the case of corn, tailings include kernels, which remain attached to a piece of cob. To enhance the effectiveness of the combine, the tailings are recycled by returning them to the threshing section for rethreshing as through use of a tailings elevator.
The volume or amount of tailings being recycled depends on the efficiency of the threshing and cleaning sections of the combine. Efficiency of the threshing and cleaning sections is determined by such factors as the clearances provided between the threshing cylinder and housing, threshing speed, the adjustment of the sieves, the output of the cleaning fan, and the volume of crop material input into the combine. If the volume or amount of tailings presented for return is excessive, the combine will tend to “plug up” with grain. That is, as the machine becomes full, the drive system used to transfer rotary power between components begins to slip thus presenting significant operating problems for the operator. When the combine does plug up, however, the operator needs to spend valuable harvesting time returning it to proper operating order. Besides the significant loss of valuable harvesting time, when a combine plugs up serious and costly damage can occur to the combine.
To solve the problem of excessive tailings, the operator can reduce ground speed of the combine, thus presenting less crop material for threshing. As will be appreciated, this is not a feasible solution to the problem because slowing the speed of the combine likewise means less efficiency. Alternatively, the operator can adjust the sieves to reduce the volume of tailings. Sieve adjustment, however, is a subjective process for the operator. That is, the operator can not be sure whether the adjustment chosen is correct before the machine is again plugged up. Alternatively, if the adjustment is incorrect, and although the tailings volume may be reduced, there may be significant contamination of the clean grain as a result of the sieves being incorrectly adjusted. Moreover, adjustment of the sieves is a time consuming process which may or may not be required depending upon several factors including the dryness of the crop material.
To solve this problem, a system of monitoring and displaying the quantity of tailings was disclosed in U.S. Pat. No. 6,053,811. In this system, a sensing device located near the tailings auger at the rear of the combine generated a signal indicative of the quantity of tailings that were created. An electronic display showed the quantity of tailings on a display for the operator to monitor.
The tailings sensing device was susceptible to vibration and other sources of electrical signal noise, however, making it difficult to provide a steady reading indicating the actual tailings volume.
What is needed is an improved system of measuring the quantity of tailings that is less susceptible to vibration, uneven tailings flow and other noise sources than previous sensing devices.